From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756061AbYICXbR (ORCPT ); Wed, 3 Sep 2008 19:31:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752904AbYICXbF (ORCPT ); Wed, 3 Sep 2008 19:31:05 -0400 Received: from chmailsrv.int.mrv.com ([66.43.110.11]:26672 "EHLO chmailsrv.int.mrv.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751944AbYICXbE (ORCPT ); Wed, 3 Sep 2008 19:31:04 -0400 Date: Wed, 3 Sep 2008 16:30:56 -0700 From: Nye Liu To: Andrew Morton Cc: nyet@nyet.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] INITRAMFS: Add option to preserve mtime from INITRAMFS cpio images Message-ID: <20080903233056.GA17404@mrv.com> References: <20080805195232.GA5183@curtisfong.org> <20080903202938.GA9065@curtisfong.org> <20080903152231.6b82d9bf.akpm@linux-foundation.org> <20080903224130.GA16630@curtisfong.org> <20080903154840.69c049cf.akpm@linux-foundation.org> <20080903230430.GA13874@mrv.com> <20080903161955.fef7362e.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080903161955.fef7362e.akpm@linux-foundation.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-OriginalArrivalTime: 03 Sep 2008 23:32:51.0658 (UTC) FILETIME=[61EDBAA0:01C90E1D] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 03, 2008 at 04:19:55PM -0700, Andrew Morton wrote: > On Wed, 3 Sep 2008 16:04:30 -0700 > Nye Liu wrote: > > > On Wed, Sep 03, 2008 at 03:48:40PM -0700, Andrew Morton wrote: > > > On Wed, 3 Sep 2008 15:41:31 -0700 > > > Nye Liu wrote: > > > > > > > > > collected[N_ALIGN(name_len) + body_len] = '\0'; > > > > > > clean_path(collected, 0); > > > > > > sys_symlink(collected + N_ALIGN(name_len), collected); > > > > > > sys_lchown(collected, uid, gid); > > > > > > + do_lutime(collected, &mtime); > > > > > > state = SkipIt; > > > > > > next_state = Reset; > > > > > > return 0; > > > > > > @@ -466,6 +520,7 @@ static char * __init unpack_to_rootfs(char *buf, unsigned len, int check_only) > > > > > > buf += inptr; > > > > > > len -= inptr; > > > > > > } > > > > > > + dir_utime(); > > > > > > > > > > Perhaps this is the simplest implementation - I didn't check the fine > > > > > details. What's your thinking here? > > > > > > > > > > > > > The main problem is that i need to save off the entire list for later > > > > processing of the directory mtimes... if i process the directory mtimes > > > > in the same pass as the file/link mtimes, touching the directory inode > > > > when creating/modifying the file/links updates the directory mtime, and > > > > overwrites whatever mtime i set the directory to when i created it. > > > > > > > > The only solution is to do a two pass, which is why the list is > > > > necessary. If there is a better way, i did not find it :( > > > > > > > > It could be that i misunderstood your question though :) > > > > > > I'm wondering whether this code need to use `struct utimbuf' at all. > > > Or at least, as much as it does. utimbuf is more a userspace-facing > > > thing whereas in-kernel timespecs and timevals are more common. > > > > > > The code as you have it does a fair few conversions into utimbuf format > > > (both directly and via the existing functions which it calls). Would > > > it be simpler if it dealt in terms of timespecs? > > > > > > > or maybe this, this one ONLY using do_utimes() and a single wrapper > > to convert the time_t > > Getting better ;) > > > diff --git a/init/initramfs.c b/init/initramfs.c > > index 644fc01..1360a67 100644 > > --- a/init/initramfs.c > > +++ b/init/initramfs.c > > @@ -6,6 +6,7 @@ > > #include > > #include > > #include > > +#include > > > > static __initdata char *message; > > static void __init error(char *x) > > @@ -72,6 +73,51 @@ static void __init free_hash(void) > > } > > } > > > > +static long __init do_utime(char __user *filename, > > + time_t mtime) > > Please avoid wrapping things which don't need it. Hard to avoid, unless you want me composing the following every place i'm currently calling do_utime(): > > +{ > > + struct timespec t[2]; > > + > > + t[0].tv_sec = mtime; > > + t[0].tv_nsec = 0; > > + t[1].tv_sec = mtime; > > + t[1].tv_nsec = 0; > > Sub-second information is lost. It'd be nice to preserve it if we're > going to do this thing. Can't! cpio isn't that smart! > > > + return do_utimes(AT_FDCWD, filename, t, AT_SYMLINK_NOFOLLOW); > > +} > > + > > +static __initdata LIST_HEAD(dir_list); > > +struct dir_entry { > > + struct list_head list; > > + char *name; > > + time_t mtime; > > +}; > > + > > +static void __init dir_add(const char *name, time_t mtime) > > +{ > > + struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL); > > + if (!de) > > + panic("can't allocate dir_entry buffer"); > > + INIT_LIST_HEAD(&de->list); > > + de->name = kstrdup(name, GFP_KERNEL); > > Alas, kstrdup() can fail too. > > It's all a bit silly checking for kmalloc() failures at this stage in > the boot process. Particularly if all we can do is panic - we might as > well blunder ahead and dereference the NULL pointer, which gives us > just as much info as the panic. And there's not much point in handling > the allocation and continuing the boot, because the system obviously > won't be booting. > > So it'd be understandable to just omit the error-checking here, despite > my earlier mentioning of its absence ;) LOL. You're the boss. > > > + de->mtime = mtime; > > + list_add(&de->list, &dir_list); > > +} > > + > > +static void __init dir_utime(void) > > +{ > > + struct list_head *e, *tmp; > > + list_for_each_safe(e, tmp, &dir_list) { > > + struct dir_entry *de = list_entry(e, struct dir_entry, list); > > could use list_for_each_entry_safe() here. static void __init dir_utime(void) { struct dir_entry *de, *tmp; list_for_each_entry_safe(de, tmp, &dir_list, list) { list_del(de); do_utime(de->name, de->mtime); kfree(de->name); kfree(de); } } something like that? I assume list_del(de) is fine. > > + list_del(e); > > + do_utime(de->name, de->mtime); > > + kfree(de->name); > > + kfree(de); > > + } > > +} > -- Nye Liu nliu@mrv.com (818) 772-6235x248 (818) 772-0576 fax "Who would be stupid enough to quote a fictitious character?" -- Don Quixote